//反向肯定查找(后瞻)
//下面的例子意思是 \d 前面的字符一定是 [A-Z]
console.log('A1a'.match(/(?<=[A-Z])\d[a-z]/)); //[ '1a', index: 1, input: 'A1a', groups: undefined ]
console.log('A1a'.match(/(?<=[1-9])\d[a-z]/)); //null


//反向否定查找(后瞻)
//下面的例子意思是 \d 前面的字符一定不是 [1-9]
console.log('A1a'.match(/(?<![1-9])\d[a-z]/)); //[ '1a', index: 1, input: 'A1a', groups: undefined ]
